ABSTRACT
Numerous formulas have been suggested to calculate the burden, which take into account one or more of the indicated parameters; their values all fall in the range of 25 to 40 D, depending fundamentally upon the properties of the rock mass. Specific drilling is defined as the drilled hole volume or drilled hole length drilled per volume unit of rock. As in other design parameters, specific drilling is in function with the blastability of the rock. In underground operations, the increase in blasthole diameter has been limited and only in metal mining have values between 125 and 220 mm been used. In tunnel and drift driving the range goes from 32 mm to 64 mm and in bench blastings for cave excavations the normal diameter runs from 64 to 90 mm. The stiffness of the parallelepiped of rock located in front of the blastholes exerts great influence on the results of blasting.
